This paper has identified detailed climate types and their geographical extents in the Republic of Korea using MK (Modified Korean)-PRISM (Parameter-elevation Regression on Independent Slopes Model) 1×1km high-resolution grid climate data and Trewartha climate classification. When considering 60 ASOS (The Automated Synoptic Observing Systems) stations, only four climate types were identified over South Korea. Three climate types, Dca (52%), Doa (28%) and Cfa (18%), were prevalent while Dcb type was only located at Daegwallyeong. When based on a high-resolution grid climate data, six climate types were identified including Dob and E types which were not detected with ASOS stations. High-resolution grid climate data reflected better and detailed geographical characteristics. Areas occupied by Cfa climate types were located along the narrow southern and Jeju coastal areas, dedicating only 6.9% of South Korea. Trewartha climate classification was also applied to 1km×1km RCP scenarios. The most distinct feature of future climate changes based on RCPs was a larger expansion of Cfa and Doa types with a drastic reduction of Dca and Dcb, indicating that a warmer and wetter climate would be prevalent over South Korea in the latter period of this century. Even for RCP2.6, all the coastal areas, some of Seoul metropolitan area, a large part of Daegu and Gwangju metropolitan areas would be classified as Cfa. For RCP8.5, 51.5% of South Korea would be occupied by the Cfas and 25.1% by the Doas, leaving only 23.2% of Dcas.